Gamma Vacuum SPCe - Response Packet

▪ a 2-byte hex checksum matching the command packet’s actual checksum,
▪ and a carriage return terminator.
3. RESPOND: The controlling computer is in count-down timer mode waiting
for a response from the SPCe. All controllers must respond within 500
milliseconds once a valid command has been received. A valid response
could be an error code indicating that the controller is BUSY with a
previous command or an acknowledging response packet. After returning
a response packet, the unit returns to MONITOR and executes the
command. If the controlling computer needs to verify that the last
command was successful, it sends a command to the unit requesting
status feedback
9.7. Response packet
The response packet is made up of at least ve elds and contains
information to let the controlling computer know the command requested
was either recognized and accepted (STATUS = “OK”), or an error condition
occurred (STATUS = “ER”). The minimum packet also contains a RESPONSE
CODE that is used either to pass an error code (if STATUS = “ER”), or is
available for each unit to use as needed for a STATUS return of “OK”. The
minimum response packet (simple acknowledgment with no data) would
consist of the following elds and would be 12 bytes long.
Table 2. Response packet
Address space Status space Response
code
space Checksum Terminator
2 bytes 1 byte 2 bytes 1 byte 2 bytes 1 byte 2 bytes 1 byte
Note:
When a device responds to the controlling computer, that response has been
requested and is expected by the computer. For this reason, a specic “start”
character is not required in the response packet. The address of the responding unit
is included in the packet, so the controlling computer can verify it to make the data
exchange easier to view on an ASCII terminal.
Field Size Comment
1. ADDRESS of unit 2 hex characters Range 00 through FF
This eld is lled in with the hexadecimal representation of the integer address of the
unit. The range provides 255 unique addresses. The controlling computer will use this
eld to determine that the correct remote unit is responding.
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2. STATUS MNEMONIC 2 ASCII characters Either OK or ER
This eld is made up of two ASCII characters and is either OK or ER. OK indicates success
in recognizing the command. ER indicates an error condition, which can mean that the
command is invalid, or the remote unit received the command but is still busy with a
previous command. Specic information about ER is reported in the RESPONSE CODE
eld.
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